<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="./vue.js"></script>
</head>

<body>
    <div id="app">
        <h1>
            <button @click="num++">{{num}}</button>
            +
            <button @click="num2++">{{num2}}</button>
            =
            {{ num + num2 }}
        </h1>
    </div>
</body>
<script>

    Vue.createApp({
        data() {
            return {
                num: 20,
                num2: 30
            }
        },
    }).mount('#app')

</script>

</html>